Project Summary The 2019 STI and HIV World Congress comprises the 23rd biennial meeting of the International Society for Sexually Transmitted Diseases Research (ISSTDR), which is jointly held with the 20th meeting of the International Union Against Sexually Transmitted Infections (IUSTI). ISSTDR was founded in 1977 and is governed by an International Board of Directors that currently represents 6 countries. IUSTI, which is on the Roster of the United Nations Economic and Social Council and is an Official Non-Government Organization in Consultative Status with the World Health Organization, was founded in 1923 and is organised on both a global and regional basis. It is the oldest international organization with the objective of fostering international cooperation in the control of STI including HIV/AIDS. The two organizations met independently until 2013, when the first joint STI & HIV World Congress was held in Vienna, Austria; that meeting was co-chaired by Dr. Thomas Quinn of the NIH and Johns Hopkins and received critical support from the NIH Division of AIDS. The STI & HIV World Congress marries cutting-edge and highly topical research themes with critical public health policy decisions in the fields of STI and HIV/AIDS. STIs, in particular syphilis, gonorrhea and chlamydia, are frequently acquired concurrently with HIV and are increasingly occurring in persons living with HIV; these STIs also increase the acquisition and transmission of HIV. Thus, HIV elimination strategies benefit significantly from consideration of the impact of STI/HIV co-infections, and joint approaches to control both epidemics. As such, the STI & HIV World Congress is the major forum for cross-disciplinary discussions among leading experts on optimal strategies for decreasing the public health burden of STIs and HIV worldwide. ! !